1. Field of the Invention
This invention relates to a floating precision current source circuit for use as a precision current reference with circuits such as analog-to-digital converter circuits, et al., this invention circuit having particular advantage when used with multi-channel Analog-to-Digital Converter Systems requiring high precision and very low drift.
2. Description of the Prior Art
Prior art current sources circuits applicable for use in precision Analog-to-Digital converters, and other uses, are typically designed to be either a floating type with an internal reference source or, a non-floating type, with an external reference source. The non-floating type using an externally referenced source has the advantage of allowing multiple stages to be referenced from a common external reference source. However, precision digital-to-analog converters having the best bias offset and drift performance typically require the use of current source of the floating type for each channel. The drift characteristics of each respective channel in these systems is influenced by the drift of the precision current source, the drift of each precision current source in turn being dependent on the drift characteristics of as many as five resistors in each current source circuit as well as the respective voltage source for the channel.